The present invention is directed generally to photoresponsive, or photoconductive imaging members, and more specifically to photoconductive imaging members comprised of certain polycarbonate resin binders. One embodiment of the present invention is directed to an imaging member comprised of a supporting substrate, a photogenerating layer in contact therewith, and a charge, especially hole, transport layer thereover, and wherein the transport layer and/or photogenerating pigment is dispersed in polycarbonates obtained from cyclic oligomers. The present invention also relates to processes for the preparation of imaging members without solvents in embodiments, wherein the polycarbonate resin binder is formed simultaneously with the charge transport and/or photogenerating layer. Imaging members of the present Invention can be sensitive to wavelengths of from about 400 to about 800 nanometers, that is from the visible region to the near infrared wavelength region of the light spectrum. Moreover, in embodiments thereof the imaging members of the present invention possess low dark decay characteristics as illustrated herein and enable developed images, both line and solid areas, of high resolution, that is with substantially no background deposits. The imaging members of the present invention can be selected for electrophotographic, especially xerographic imaging and printing systems.
Layered photoconductive imaging members with certain polycarbonate resin binders are known. One layered photoresponsive device has been described in U.S. Pat. No. 4,265,990, the disclosure of which is totally incorporated herein by reference. Photoresponsive materials containing a hole injecting layer overcoated with a hole transport layer, followed by an overcoating of a photogenerating layer, and a top coating of an insulating organic resin, are disclosed in U.S. Pat. No. 4,251,612, the disclosure of which is totally incorporated herein by reference. Examples of photogenerating layers disclosed in these patents include trigonal selenium and phthalocyanines, while examples of transport layers include certain aryl diamines as illustrated therein- These imaging members are usually prepared by first providing on a supporting substrate a photogenerating layer of, for example, trigonal selenium and thereafter solution coating thereover from a solvent mixture a charge transport layer and a polycarbonate resin, such as MAKROLON.RTM.. Thus the polycarbonate resin binder is in the form of a polymer when selected for the preparation of the imaging member. With the invention of the present invention, in embodiments there is selected a monomer and this monomer is converted into a polymer simultaneously with the coating of the charge transport layer. Advantages of the aforementioned include, for example, the use of solvents like toluene or tetrahydrofuran, rather than the toxic and environmentally damaging chlorinated, such as methylene chloride, organic solvents to form a coating. Since solution viscosity is proportional to molecular weight, and it is the coating solution viscosity that determines the concentration for any given coating technique, the use of higher solid loadings in the coating solution is readily achievable as the cyclic oligomer precursor to the polycarbonate polymer possesses a much lower by, for example, orders, such as 10, of magnitude solution viscosity than the polymer itself, thus higher solid loadings are desirable to reduce volatile organic concentrations emitted during the coating process. The processes of the present invention and imaging members thereof allow the transport binder to be optionally crosslinked to provide tougher and more solvent resistant coatings. Also provided in embodiments are higher, 100,000 to 300,000 vs about 40,000, for spray coating molecular weight polycarbonate films formed using spray or dip coating techniques than can be achieved with a polymer solution. The use of a solvent for forming a photoreceptor film may be avoided entirely with the present Invention in embodiments by coating the cyclic oligomers and transport molecule mixture as a melt or a powder before curing the cyclic oligomers to provide a high molecular weight polymer. Additionally, by using mixtures of different structured cyclic oligomers high molecular copolymers of exact stoichiometry can be obtained that are not readily obtained by either the known interfacial or melt transesterification processes for producing polycarbonates.
Documents illustrating layered organic electrophotographic photoconductor elements with azo, bisazo, and related compound, and in some instances charge transport layers dispersed in certain polycarbonates, and wherein the charge transport layer can be applied to the photogenerating layer by solution coating include U.S. Pat. No. 4,390,611, U.S. Pat. No. 4,551,404, U.S. Pat. No. 4,996,754, Japanese Patent 60-4354, U.S. Pat. No. 4,400,455, U.S. Pat. No. 4,390,608, U.S. Pat. No. 4,327,168, U.S. Pat. No. 4,299,896, U.S. Pat. No. 4,314,015, U.S. Pat. No. 4,486,522, U.S. Pat. No. 4,486,519, U.S. Pat. No. 4,955,667, U.S. Pat. No. 4,440,845, U.S. Pat. No. 4,486,800, U.S. Pat. No. 4,309,611, U.S. Pat. No. 4,418,133, U.S. Pat. No. 4,293,628, U.S. Pat. No. 4,427,753, U.S. Pat. No. 4,495,264, U.S. Pat. No. 4,359,513, U.S. Pat. No. 3,898,084, U.S. Pat. No. 4,830,944, U.S. Pat. No. 4,820,602, and U.S. Pat. No. 3,989,084, the disclosures of which are totally incorporated herein by reference.